Is Photosynthesis Irreducibly Complex?
|April 14, 2007||Posted by idnet.com.au under Intelligent Design|
From Nature this week. “Knowing how plants and bacteria harvest light for photosynthesis so efficiently could provide a clean solution to mankind’s energy requirements. The secret, it seems, may be the coherent application of quantum principles. Roseanne J. Sension doi:10.1038/446740a Full TextÃ‚Â
Photosynthesis provides the primary energy source for almost all life on Earth. One of its remarkable features is the efficiency with which energy is transferred within the light harvesting complexes comprising the photosynthetic apparatus. Suspicions that quantum trickery might be involved in the energy transfer processes at the core of photosynthesis are now confirmed by a new spectroscopic study. The study reveals electronic quantum beats characteristic of wavelike energy motion within the bacteriochlorophyll complex from the green sulphur bacterium Chlorobium tepidum. This wavelike characteristic of the energy transfer process can explain the extreme efficiency of photosynthesis, in that vast areas of phase space can be sampled effectively to find the most efficient path for energy transfer.
Photosynthetic complexes are exquisitely tuned to capture solar light efficiently, and then transmit the excitation energy to reaction centres, where long term energy storage is initiated. The energy transfer mechanism is often described by semiclassical models that invoke ‘hopping’ of excited-state populations along discrete energy levels 1, 2. Spectroscopic data clearly document the dependence of the dominant energy transport pathways on the spatial properties of the excited-state wavefunctions of the whole bacteriochlorophyll complex 6, 10. Here we obtain direct evidence for remarkably long-lived electronic quantum coherence playing an important part in energy transfer processes within this system. The quantum coherence manifests itself in characteristic, directly observable quantum beating signals among the excitons within the Chlorobium tepidum FMO complex at 77Ã‚Â K. This wavelike characteristic of the energy transfer within the photosynthetic complex can explain its extreme efficiency, in that it allows the complexes to sample vast areas of phase space to find the most efficient path.Ã‚Â Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems Gregory S. Engel et al Nature 446, 782-786 (12 April 2007) | doi:10.1038/nature05678″
Conclusion? Obviously this is a brilliant piece of design by someone who evenÃ‚Â knows how quantum mechanics works. Well not exactlyÃ‚Â …
Photosynthesis Analysis Shows Work Of Ancient Genetic EngineeringÃ‚Â
Science Daily 2002 Ã¢â‚¬â€ The development of the biochemical process of photosynthesis is one of nature’s most important events, but how did it actually happen? This is a question that molecular biology has first posed, and now perhaps answered.
“The process of photosynthesis is aÃ‚Â very complex set of interdependent metabolic pathways,” said Robert Blankenship, professor of biochemistry at Arizona State University. “How it could have evolved is a bit mysterious.”
Photosynthesis is one of the most important chemical processes ever developed by life — a chemical process that transforms sunlight into chemical energy, ultimately powering virtually all the living things and allowing them to dominate the earth. The evolution of aerobic photosynthesis in bacteria is also the most likely reason for the development of an oxygen-rich atmosphere that transformed the chemistry of the Earth billions of years ago, further triggering the evolution of complex life. After decades of research, biochemists now understand that this critical biological process depends on some very elaborate and rapid chemistry involving a series of enormously large and complex molecules a set of complex molecular systems all working together.
“We know that the process evolved in bacteria, probably before 2.5 billion years ago, but the history of photosynthesis’s development is very hard to trace,” said Blankenship.
In a paper in the November 22 2002 issue of Science, Blankenship and colleagues partially unravel this mystery through an analysis of the genomes of five bacteria representing the basic groups of photosynthetic bacteria and the complete range of known photosynthetic processes.
The analysis revealed clear evidence that photosynthesis did not evolve through a linear path of steady change and growing complexity but through a merging of evolutionary lines that brought together independently evolving chemical systems — the swapping of blocks of genetic material among bacterial species known as horizontal gene transfer.
“We found that the photosynthesis-related genes in these organisms have not had all the same pathway of evolution. It’s clear evidence for horizontal gene transfer,” said Blankenship.
Blankenship performed a mathematical analysis of the set of shared genes to determine possible evolutionary relationships between them, but they arrived at different results depending on which genes were tested
“We did a kind of tree analysis of all 188 genes to determine what the best evolutionary tree was. We found that a fraction of the genes supported each of the different possible arrangements of the tree. It’s clear that the genes themselves have different evolutionary histories,” Blankenship said.
Blankenship argues that different pieces of the system evolved separately in different organisms, perhaps to serve purposes different from their current function in the photosynthesis. Brought together either by fusion of two different bacteria or by the “recruitment” of blocks of genes, the new combination of genes resulted in a new combined system.
“This kind of evolution in bacteria is kind of like what happens at a junk dealer,” said Blankenship.
“Bits and pieces of whatever there is out in the yard get hauled back and welded together and made into this new thing. All these metabolic pathways get borrowed and bent a bit and changed.”
Blankenship points out that nature’s way of creating useful and complicated chemical systems through horizontal gene transfer also points to how human-directed biodesign might co-opt the process.
“This work gives us some insights into how complex metabolic pathways originated and evolved, so this might give some ideas about how to engineer new pathways into microorganisms,” he said. “These organisms could be designed to carry out new types of chemistry that may benefit mankind, such as multi-step synthesis of drugs.”
How exactly did all those different organisms, who donated parts of the photosynthesetic process, get their energy while they were doing all that evolving of the components of the Irreducibly Complex looking system ready to be put together by the Blind Watchmaker?